The Correction of Myopia Evaluation Trial (COMET), a multi-center, randomized clinical trial designed to evaluate whether progressive addition lenses (PALs) slow the progression of myopia compared to single vision lenses (SVLs), enrolled 469 myopic children who have been carefully followed with annual standardized measurements of myopia by cycloplegic autorefraction and axial length over a 3-year period. Retention has been excellent, with 98.5% of children completing 3-year follow-up visits. Four year follow up visits will be completed in October, 2002, and soon after that the study design will shift from a clinical trial to a longitudinal investigation. The COMET cohort provides a unique opportunity to characterize myopia progression and how it is influenced by factors identified in the first phase of COMET as well as new data on familial myopia, including genetic analyses. Better understanding of the factors predictive of myopia progression and stabilization also will help guide selection and timing of interventions as well as target those groups that may benefit most from treatment. COMET-Phase II will accomplish the following aims by collecting data from COMET children for an additional 5 years. Aim 1: To develop predictive models and identify factors that characterize changes over a 9 - year period in myopia and axial length, based on the cohort of children in COMET. Aim 2: To complete ascertainment of the pedigrees of COMET families and to conduct studies designed to investigate genetic loci for juvenile-onset myopia, beginning with those previously identified for high myopia. Aim 3: To evaluate the long term effect (i.e., beyond three years) of having worn either PALs or SVLs for at least three years. This application seeks continued support for the activities of the Coordinating Center. The major responsibilities of the Coordinating Center will continue to be to: 1) provide epidemiologic and biostatistical expertise to the design, conduct and analysis of Phase II; 2) develop and implement the statistical analysis plan including genetic analyses; 3) collaborate in the development, modification and distribution of forms, documents and protocols; 4) be responsible for data management; processing and analysis; 5) prepare reports to monitor recruitment, data collection, and data quality; 6) coordinate and document communications among clinical centers; 7) be responsible for quality assurance procedures; and 8) collaborate in preparing publications of the results. Additional aims for Phase II are to: 1) model the progression and stabilization of myopia in COMET children; 2) track the flow of parental/sibling refractive error and genetic data among study centers; and 3) create the pedigree structure, establish the genetic database and conduct linkage, and other genetic analyses.